This invention relates generally to the separation of isotopes from each other and particularly relates to a more inexpensive way for separating isotopes in a substantially neutral, dense plasma.
Presently the principal means for separating uranium isotopes on a commercial basis is the gaseous diffusion process. In order to increase the capacity of such diffusion plants a heavy capital investment is required which may be on the order of many hundred million dollars per year.
On the other hand, in recent years research in many countries and by many people has produced a vastly superior knowledge and insight into the nature of plasmas. Particularly, our knowledge of the behavior of dense plasma has been much increased. Isotope separation in a dense plasma should permit the separation of much larger quantities of the desired isotopes at much lower cost and with less expenditure of energy. Furthermore, separation of isotopes in a dense plasma is facilitated by the fact that plasma devices exist which can be used for similar processes. Among these devices are the so-called Q-machines.
It is well known that a beam of charged particles cannot exceed a certain density because the charged particles tend to repel each other. On the other hand, in a neutral plasma no matter how dense, individual charged particles are neutralized by other particles of opposite charge. Therefore, a plasma can be made much denser than a charged beam.
It will be evident that a less expensive method for separating isotopes will make it possible to utilize isotopes for purposes which in the past have simply been too expensive. For example, such isotopes may have many uses in medicine. They may also be useful for light sources generating monochromatic light, that is light generated by a single isotope of a suitable element. Similarly, it may be desirable to manufacture lasers containing as a laserable material a single isotope of a suitable element. Single isotopes may also be used for nuclear reactors. In this case it may be desirable to utilize a special isotope which has the best neutron properties for the reactor such as an especially large or small neutron absorption cross-section.
Various methods have been suggested in the past for separating isotopes besides the gaseous diffusion process. Among these methods are the use of a laser for exciting a particular energy level of one isotope without exciting the other isotopes. This may require a tunable laser for optically exciting say the uranium isotope 235 preferentially over the 238 uranium isotope. The excited uranium atom may now be more readily ionized as distinguished from the unexcited ion so that a separation of the charged and neutral isotopes can easily be carried out. Such a separating method has been described, for example, in the patent to Pressman, U.S. Pat. No. 3,558,877. A similar two photon scheme for exciting and subsequently ionizing a selected isotope has been described in the patent to Levy et al., U.S. Pat. No. 3,772,519. The use of a laser to cause ionization of a gas by the electric field caused by a focused laser beam has been disclosed in the patent to Brubaker et al. 3,478,204.
Also, the use of laser beams for the formation of plasma or for bombarding microparticles has been suggested in the patents to Vali et al., U.S. Pat. No. 3,360,733 and Hansen et al., U.S. Pat. No. 3,679,897.
Plasma confining devices having magnetic mirrors are well known in the art. An example of such a patent is the patent to Delcroix et al., U.S. Pat. No. 3,257,579. The use of a diverging magnetic field, sometimes called a magnetic nozzle, has been proposed for the separation of at least two isotopes in the patent to Roehling, U.S. Pat. No. 3,845,300.
Finally, reference is made to a paper by Hidekuma et al. which appears in Physical Review Letters of Dec. 23, 1974, Volume 33, No. 26, pages 1537 - 1540. This paper proposes to plug or retain desired ion species and permit the others to escape from a container. This is effected by a magnetic cusp created by suitable magnetic fields. The purpose of the experiment was to permit impurities contained in the reactor to escape while retaining the desired particles.
It is therefore an object of the present invention to provide a novel method of and apparatus for the separation of isotopes of various elements which is substantially less expensive than presently known methods.
Another object of the present invention is to provide a novel process for separating isotopes making use of a plasma of relatively large density, thereby increasing the yield of such a method.
A further object of the present invention is to provide a method of and apparatus for separating isotopes which is applicable to many elements having more than one isotope.